The invention relates to improvements to a horizontal continuous substrate treatment plant for the treatment, for example coating, of slab-shaped substrates, for example glass panels, wherein the substrates, with or without substrate mounts, lying on a conveying unit, i.e. in a horizontal orientation, are conveyed through a plant chamber delimited by chamber walls or an arrangement of a plurality of plant chambers arranged behind one another of a substrate treatment plant, wherein the substrates are subjected to the effect of at least one substrate treatment unit, such as, for example, coating units, etching units, etc. The substrate treatment, on the one hand, often takes place under a pressure which is lower than the atmospheric pressure (process vacuum), and, on the other hand, also oftentimes in a selected gas or gas mixture which is often introduced in a controlled manner (process atmosphere).
In contrast to what are referred to as batch substrate treatment plants, in continuous substrate treatment plants generally at least in each case a plant chamber, which is configured as a lock chamber, is located upstream and downstream of the plant chamber or an arrangement of a plurality of plant chambers arranged behind one another, which may be configured as, for example, process chambers, pump chambers, transfer chambers, etc., and a conveying unit is located inside the substrate treatment plant such that said conveying unit extends through the two lock chambers and through all other plant chambers located in between.
As a result, substrates can be moved in a conveying direction through the substrate treatment plant in that they are introduced into the substrate treatment plant by means of a first lock chamber, conveyed through the entire arrangement of plant chambers arranged behind one another by means of the conveying unit, and are evacuated from the substrate treatment plant by means of a second lock chamber. Here, the substrates in at least one process chamber are also moved past a substrate treatment unit located in said process chamber and thereby subjected to the required substrate treatment.
For the treatment of slab-shaped substrates, conveying units have proven successful which comprise a plurality of rotatably mounted, cylindrical conveying rollers transversely arranged to the conveying direction of the substrates, the topmost generatrices of said conveying rollers defining a horizontal conveying plane for the substrates, and at least some of said conveying rollers being drivable. In the event that the required substrate treatment takes place under elevated process temperatures, for example 400, 600 or 800° C., it has proven successful to manufacture the conveying rollers from heat-resistant materials, for example ceramics, or to coat them with a heat-resistant material.
For the coating of, for example, slab-shaped substrates, various vapor sources are known. The vapor source, or a vapor distributor connected to a vapor source, in a plant of the type described above may be arranged for example transversely to the conveying direction of the substrate such that an approx. 5 cm wide region of the substrate is impinged transversely across the width of the substrate by vapor.
The coating material may, for example, be carried to the location of vaporization in powder form by means of a carrier gas. The crucible of the vapor source which implements the melting and vaporization of the coating material may, for example, be formed by heated ceramic pipes. The crucible itself may, for example, have vapor outlet openings and thus simultaneously serve as vapor distributor. Alternatively, additional vapor distributors which are connected to the crucible or crucibles in a vapor-conducting manner may handle the task of directing the coating material from the vapor source towards the substrate. This leads to a distribution of the vapor in the entire coating region of the plant. A kind of mist is created which disseminates in the coating region of the plant, for example in what is referred to as a compartment.
An exemplary compartment may contain, for example, 12 conveying rollers, while the vapor source including suction pipes takes up the space of four conveying rollers. Suction pipes are located on both sides of the vapor source. Said suction pipes extract mainly the carrier gas from the compartment, but are unable to develop sufficient suction to have any effect on the mist.
One problem as a result of the mist is the unintentional coating of all components which are somewhat colder (e.g. below 600° C.), since the coating material condenses there (predominantly conveying rollers and chamber walls). The conveying rollers, which develop into what is referred to as “dog bones”, become increasingly unsuitable through time for conveying a substrate. They, too, need to be cleaned or replaced.
In co-pending, unpublished German patent application DE 10 2013 206 598, assigned to the assignee of this patent application, known coating units and vacuum coating plants are improved with a view to preventing contamination and damage to layers produced on the surface of the substrate to be coated.
To this end, in a coating unit for a vacuum coating plant, which comprises a heatable vapor source for holding and vaporizing a coating material and at least one vapor outlet opening, the latter being configured such that it imparts a central vapor outlet direction to the evaporated coating material, it is proposed that the central vapor outlet direction is unequal to the gravitational direction. In order to prevent falling flakes of condensed coating material from hitting the substrate, it may be provided that a collection means for falling condensate is located below the at least one vapor outlet opening. This collection means, which is preferably configured as a pan arranged far from the outlet opening, for example immediately above the substrate, or as a conveying element which is transversely movable to the conveying direction, ensures that the flakes neither damage nor contaminate the layer of condensed coating material deposited on the substrate.
The present invention relates to a substrate treatment plant, as illustrated in FIG. 1, comprising a process chamber delimited by chamber walls 11 and in the process chamber a substrate conveying unit for the horizontal conveyance of slab-shaped substrates 3 in one conveying plane and in one conveying direction, wherein the substrate conveying unit comprises an arrangement of rotatably mounted, cylindrical conveying rollers 4 transversely arranged to the conveying direction, the topmost generatrices of said conveying rollers defining the conveying plane, and at least one substrate treatment unit 1, which is located above the conveying plane, and at least one gas inlet.
It is known that in the region of a substrate treatment unit 1 undesirable coatings are deposited on conveying rollers 4 in a process chamber delimited by process chamber walls, which process chamber for the generation of elevated process temperatures may have a heating device 5, wherein the process chamber walls are protected from the elevated process temperatures by means of a heat protective insulation 2, this deposition occurring as soon as the gap in the substrate is located below the substrate treatment unit and the conveying rollers are thus briefly exposed to a particle stream of the substrate treatment unit. The substrate treatment unit 1 may, for example, be configured as a magnetron for sputtering a material, or as a vapor source, or any other unit for depositing a material on a substrate. A process chamber having a substrate treatment unit with heating devices 5 in each case located above and below the conveying rollers 4, and thermal insulation 2, is illustrated at least section-wise in FIG. 1. By way of example, if a vaporization with carrier gas takes place, impulses of the vapor particles with the carrier gas occur, and the particles may in part also reach the conveying roller regions below the substrate, in particular the regions beside and under the edge of the substrate along the conveying direction. Even if the conveying rollers are configured as drums, the vapor particles reach in particular the ends of the drums, and a layered growth referred to as “dog bone” may form on the conveying rollers.
On account of the coatings of various thickness on the conveying rollers, conveying problems may occur, since the substrates no longer lie with their entire surface on the conveying rollers, as a result of which positive guiding of the substrates is no longer possible and deviations from the straight running of the substrates through the process chamber occur.
As a result of the diameter increase of the conveying rollers on account of the undesirable coating, higher circumferential speeds of the conveying rollers beneath the substrate treatment unit and thus an increase in the conveying speed and thus a variation in the layer thicknesses along the conveying direction of the substrates occur.